Watercraft powered by inboard or outboard motors typically include an electrical system. The motor includes a water propulsion device which is powered by an internal combustion engine. As is well known, an ignition system is utilized to fire one or more ignition elements corresponding to each combustion chamber of the engine, igniting the air and fuel mixture in each combustion chamber of the engine.
These engines commonly include a liquid cooling system. Liquid coolant in the form of water in which the watercraft is operating is supplied to various cooling passages or jackets associated with the engine. In some instances, the cooling system is arranged such that the coolant drains from the coolant jackets when the engine is stopped.
In order to prevent engine overheating, an overheat detection system may be associated with the engine. The detection system includes a sensor for sensing the temperature of the engine. The output of the sensor may be used by an engine control unit to shut off the engine by disabling the ignition system.
This system has the drawback that at certain times a condition of engine overheat may be indicated when in fact the engine is not in an overheat condition. Referring to FIG. 12, when the engine is operating normally and coolant is in the water jacket(s), the temperature inside the water jacket Tw remains lower than a predetermined high temperature Tlim. When the engine is shut off, however, the coolant drains from the jacket and the temperature in the jacket rises. The temperature may rise to a point well above the predetermine high temperature Tlim.
If the engine is subsequently restarted before the temperature in the jacket falls back below the temperature Tlim, the overheat detection system will indicate that the engine is overheated. This is due primarily because coolant is not yet being supplied to the cooling jacket(s).
An improved engine overheat detection system which overcomes the above-stated problems is desired.